1. Field of the Invention
The invention lies in the field of medical technology or dentistry and relates to an implant and to a method of preparing an implant for implantation. It further relates to a kit of parts for carrying out the method and to an implantation method. The implant according to the invention is suitable for being implanted in human or animal tissue, in particular in hard tissue such as bone, but it is also suitable for being fixed in a natural tooth, i.e. to a dentine or enamel surface. Although in the latter case one skilled in the art would not refer to an “implant” and to “implantation method”, these terms are used in the following as including elements and methods suitable for endodontic use.
2. Description of Related Art
In WO 02/069 817, a method of implanting an implant in human or animal tissue has been disclosed. The implant includes surface regions of a material liquefiable by mechanical vibration. The liquefiable material is in contact or can be brought into contact with the tissue part in a region in which the tissue part has surface unevennesses or openings or in which such surface unevenesses or openings can be created by hydrostatic pressure. The implant is then impinged with mechanical vibration and simultaneously pressed against the tissue part until at least a part of the liquefiable material is liquefied and is pressed into said surface unevennesses or openings. Thereafter, the liquefiable material is let to re-solidify, while the implant is still pressed against the tissue part. WO-04/017927 discloses a similar method for fixing elements, e.g. fillings or root pins, in parts of natural teeth.
The basic principle of the above named methods has been proven to be successful in surgery and dentistry, especially for fixing an implant in bone tissue or a corresponding element in the dentine or enamel of a tooth. The liquefiable material—often being a thermoplastic—after re-solidification, provides substantial primary stability of the connection between the implant and the bone tissue.
In order to provide sufficient conductivity of mechanical vibration energy from a proximal to a distal end of the implant and to achieve a sufficient primary stability, the liquefiable thermoplastic material has to be of a certain minimal stiffness. Generally, the modulus of elasticity (Young's modulus) should be 0.5 GPa or higher. A not too low modulus of elasticity is also necessary for the mechanical vibrations to be conducted through the thermoplastic material to the surface portion which is in contact with the tissue. However, a high modulus of elasticity adversely affects the thermoplastic material's capability of absorbing mechanical energy (absorptivity). More concretely, the absorptivity is proportional to the square of the strain induced in the material by the mechanical vibration, which strain for a given power is the higher, the softer the material. Therefore, for materials with a high modulus of elasticity the local friction between the vibrating thermoplastic material and the tissue plays an important role in the liquefying process.
However, for implanting into soft or brittle tissue—such as osteoporotic bone tissue—it is hardly possible to exploit such friction, since it is not possible to excerpt the necessary force to the tissue. The possible frictional force is also limited by the contact area between tissue and implant surface, which contact area is reduced for spongy tissue with large cavities in the tissue material.